1. Field of the Invention
One or more embodiments of the present invention relate to an encoding and/or decoding of an audio signal, and more particularly, to a method, medium, and apparatus encoding and/or decoding an audio signal for minimization of the size of codebooks used in encoding or decoding of audio data.
2. Description of the Related Art
As digital signal processing technologies advance, most audio signals are being stored and played back as digital data. Digital audio storage and/or playback devices sample and quantize analog audio signals, transform the analog audio signals into pulse code modulation (PCM) audio data, which is a digital signal, and store the PCM audio data in an information storage medium, such as a compact disc (CD), a digital versatile disc (DVD), or the like, so that a user can reproduce the stored audio data from the information storage medium when he/she desires. Digital audio signal storage and/or reproduction techniques have considerably improved sound quality and remarkably reduced the deterioration of sound caused by long storage periods, compared to analog audio signal storage and/or reproduction methods, such as conventional long-play (LP) records, magnetic tapes, or the like. However, this has also resulted in large amounts of digital audio data, which sometimes poses a problem for storage and transmission.
In order to solve these problems, a wide variety of compression techniques have been implemented for reducing/compressing the digital audio data so more audio data can be stored or the stored audio data takes up less recording space. Moving Picture Expert Group audio standards, drafted by the International Standard Organization (ISO), and AC-2/AC-3 technologies, developed by Dolby, have adopted techniques for reducing/compressing the size of the audio data using psychoacoustic models, which results in an effective reduction in the size of the audio data regardless of the individual characteristics of underlying audio signals.
Conventionally, for entropy encoding and decoding during encoding of a transformed and quantized audio signal, context-based encoding and decoding have been used. To this end, these conventional techniques require a corresponding codebook for the context-based encoding and decoding, which requires a large amount of memory.